This invention relates generally to rotatable disc cuvette arrays and assemblies adapted for use in a centrifugal fast analyzer having means to centrifugally rotate the array in order to produce measurements of the optical density or absorbance values of a light path passing successively through each of a series of radially spaced cuvettes during their rotation. Such systems are in wide use, particularly for absorbance measurements utilized with analytical apparatus.
More specifically, these fast analyzers are generally furnished with an array usually having individual inner and outer compartments for each of the cuvettes. These compartments are physically separated from each other by a wall such as an annular ramp which divides each cuvette into these inner and outer compartments and prevents fluid communication therebetween prior to centrifugation. Such arrays have a structure wherein a central hub portion has positioned outwardly thereof a selected number of radially disposed cuvettes. Normally each of the individual cuvettes are radially positioned side by side and have a common radially extending dividing wall between each pair of adjacent cuvettes to form the disc portion of the assembly into the rotatable cuvette array. The inner compartments usually comprise a holding means for whatever reagents or reactants which are placed therein prior to the centrifugation run and read cycle. The outer compartments are also formed into an annular ring, spaced radially outward from the inner compartments, and are divided therefrom prior to centrifugation by the described wall or walls, preferably ramp-shaped in form and having an inner vertical wall which preferably has an inclination in the vertical plane of approximately 40.degree. to 60.degree. degrees, so as to form the desired ramp angle between the inner and outer compartments.
Such rotary cuvette assemblies are particularly adapted for use in a clinical analyzer in their most common useage, in order to produce a reaction between the material contained within the inner compartment and that material which is contained in the outer compartment, the latter usually comprising an unknown sample, for example, a body fluid. The most common use of these analyses is the determination of blood or blood plasma or serum components, the blood forming the sample, or unknown, material under test and being deposited in the outer ring of compartments. Upon centrifugation the reagent or reactant materials contained in the inner compartments, diluted if desired to a fixed concentration and/or pH, are thrown outwardly and rise over the inner inclined walls or ramps of the cuvette compartment dividers and then flow into the outer chambers where they intimately contact and mix with the materials contained in the chambers. Typically, the parameters of the blood or other material contained in the outer compartments, as well as those of the materials contained within the inner compartments, are carefully fixed as to volume, temperature, acidity, etc., and have been treated prior to use for removal of fibrins or similar debris which would have an adverse effect upon the reaction and upon the uniformity and light tramsmission characteristics of the measured optical density of the materials when they become mixed in the outer compartments. In many instances in the prior art there has been used an assembly of rotary cuvettes which is provided with an additional radially aligned chamber, or compartment, for each of the individual cuvettes, the third compartments being spaced radially outwardly from the second compartments, so as to form a third annular ring of compartments. Where this is done, an additional annular compartment separating or partition wall, which may also be of the slope or ramp type, provides the separation means between the second annular series of cuvette compartments and the outermost third series of compartments of the overall assembly. In this latter type of prior art three-compartment duvettes, the reaction takes place for the most part in the third compartment, although in some analytical or other reactions a portion of the reaction will occur while the materials from the first, most inwardly positioned compartments are flowing in partially mixed form with the materials from the second compartments prior to the combined flow reaching the third compartments.
Although the centrifugation speeds generally used with such analyzers, particularly for clinical analysis, are not of such great magnitude as to fall within the ultra centrifugation range of 20,000 rpm or more, the usual fast analyzer rotor speed is sufficient so that the mixed materials will generally be centrifugally forced into a vertical layer against the outer vertical walls which form the final vertical wall of the overall cuvettes. Preferably, as stated above, the cuvettes are physically made as identical as is possible in so far as each component part thereof is concerned.
In order to avoid spillage, or to minimize the possibility of spillage of the materials during the run, the heights of the dividing ramps are so selected relative to the greater height of the radial walls which divide the cuvettes from each other, and which form the side walls of each of the compartments of the cuvettes, that such spillage is avoided without undue interference with the travel of the materials to their most radially outward position, where the components from the inner compartments are mixed and form a substantially vertical layer against the vertical outer wall of each of the cuvettes. During the centrifugal run the cover seal and the joints between the parts are subjected to the greatest forces tending to cause spillage or leakage.
For details of the use of such apparatus, and disclosures of various processes which can be carried out thereby, reference is made to the following patents which disclose such curvette arrays utilized in a clinical, electronically corrected, interfaced fast analyzer, generally known as small or miniature fast analyzers, such apparatus and systems originally having been developed for the most part by the Oak Ridge National Research Laboratory of the Nuclear Regulatory Commission of the Energy Research Development Agency, this commission formerly being known as the United States Atomic Energy Commission, and the original large scale analyzers produced thereby having been known as GeMSAEC analyzers: Norman G. Anderson Pat. Nos. 3,536,106, 3,547,547, 3,555,284, 3,582,218, 3,586,484, 3,798,459; Mailen U.S. Pat. No. 3,744,975; Tiffany el al., U.S. Pat. No. 3,763,374; Scott et al., U.S. Pat. No. 3,800,161; Mullaney et al., U.S. Pat. No. 3,824,402; Hinman, U.S. Pat. No. 3,863,049.
Additionally, details of such prior art structures and processes for using the same are shown and described in detail in many literature references including the following: Basic Principles of Fast Analyzers (1971) Amer. J. Clin. Path., Vol. 53, pp. 778-785, by Norman G. Anderson; Computer Interfaced Fast Analyzers (1969) Science, Vol. 166, pp. 317-324, by Norman G. Anderson; Increased Rate of Analysis by Use of a 42-Cuvette GeMSAEC Fast Analyzer (1971) Clinical Chemistry, Vol. 17, pp. 686-695, by Burtis et al., Dynamic Introduction of Whole-Blood Samples into Fast Analyzers (1972) Clinical Chemistry, Vol. 18, pp. 749-752, by Scott et al.; Development of a Portable Data Processer With Mechanical Data Output for Use With a Miniature Fast Analyzer (1972) Clinical Chemistry, Vol. 18, pp. 762-770, by Johnson et al.; Development of an Analytical System Based Around a Miniature Fast Analyzer (1973) Clinical Chemistry, Vol. 19, pp. 895- 903, by Burtis et al.; A Miniature Fast Analyzer System (1973) Analytical Chemistry, Vol. 45, pp. 327A-340A, by Scott et al.; Optimization and Analytical Application of the Technique of Dynamic Introduction of Liquids into Centrifugal Analyzers (1974) Clinical Chemistry, Vol. 20, pp. 932-941, by Burtis et al.; A Centrifugal Analyzer With a New All-Digital Measurement System (1974) Clinical Chemistry, Vol. 20, pp. 942-949, by Avery et al., Incorporation of a High-Speed Decimal Data Processor Into a Centrifugal Analyzer (1974) Clinical Chemistry, Vol. 20, pp. 950-960, by Gregory et al.; A Small Portable Cenntrifugal Fast Analyzer System (1974) Clinical Chemistry, Vol. 20, pp. 1003-1008, by Scott et al.; Blood Grouping with a Miniature Centrifugal Fast Analyzer (1974) Clinical Chemistry, Vol. 20, pp. 1043-1057, by Tiffany et al.; Programming Concepts for the GeMSAEC Rapid Photometric Analyzer, (1974) Clinical Chemistry, Vol. 20 by Kelley et al.
In general, the prior art cited above has utilized a multi-cuvette array which essentially consists of an array composed of a plurality of pie-shaped, radially disposed cuvettes which radiate out from a central hub portion and which contain in radial order in each of the chambers or cuvettes, proceeding radially outwardly from the hub or center of the generally round, substantially disc-shaped array structure: a first annular series of chambers for initially holding a first group of reactants, an annular series of dividing walls or ramps, one for each cuvette, a second annular series of compartments for holding initially different reagents which frequently are the unknown samples of blood or other body fluids, and an outer annular series of vertical end walls.
It has generally been convenient in this prior art to form such discs with the individual cuvettes thereof being integrally united at the time of manufacture. During the reacton run the array is rotated at a speed to cause the contents of the first chambers to climb over the ramps under centrifugal force and mix and react with the materials contained in the second chambers.
On top of the cuvettes there are generally placed some form of cover means to prevent evaporation and contamination, the cover means still leaving paths for the measurement of the optical density or fluorescent emission characteristics of the reacting materials, when the array is rotated, with these openings, one for each cuvette, passing between a source of illumination, in the case of measurement of absorption, and an optical light transmission sensing means. The disc array is usually driven at speeds of between about 300 and about 500 rpm during most of such measurement run cycles after a preliminary initial fast run at higher speeds in the vicinity of 3,000 to 5,000 rpm to cause more rapid initial reaction by increasing initial reactant material contact.
The chamber in which the cuvette and other apparatus is placed and/or the cuvette array itself has its temperature controlled closely, usually by heating during an incubation period both prior to and during this run in which the reaction is occurring. The light transmission characteristics are changing as the reaction proceeds and, since the temperature affects this rate, it must be accurately controlled.
Because of the necessity for extremely accurate measurements, it is essential that all of the components of the overall fast analyzer possess parameters which should be determined with as high a degree of accuracy as possible. This desired accuracy necessity is disclosed in the above cited patents and literature references and the reasons therefor are discussed at length therein.
Even though the reactants placed in each cuvette total only small amounts measured in microliters, in the ideal, optimum, analytical systems each component of the system, including the entire optical system, the rotation motor drive speed, the means for holding the rotor, as well as the cuvette array, are all accurate to within less than 0.1 percent variation. To ensure the repetitive accuracy of the readings of the optical density through the cuvettes, it has therefore been the object of the prior art to define in the disclosed systems an apparatus in which the individual cuvettes of the array are made as identical as is possible as to parameters from cuvette-to-cuvette; and all of the parts, including the cuvette array are fixed so that minimal error variations are introduced. In order to accomplish this desired result the prior art has generally relied upon expensive cuvette array discs which are close tolerance machined in order to ensure maximum uniformity. Plastic materials of proper optical density have been suggested in the above prior art, but such systems have used, of necessity, rigid, thick plastic plates in order to be able to accurately tool-machine these plates so as to form them with the chambers and optical passages as finished components which are then assembled into a unitary cuvette array structure by means of multiple clamping plates and sealing or the like plates, into a complex multiple part assembly.
These prior art devices have usually included a solid opaque cover plate positioned over the entire array, except for an annular series of radially disposed passageways through the top cover immediately above the first or inner annular series of chambers of the cuvettes and a similar annular series of openings positioned above the second radially outwardly positioned annular series of chambers of the cuvettes. Such holes are generally relatively small and are positioned over the approximate radial centers of each of the cuvettes relative to the side walls thereof so as to provide passages for placing the materials in the chambers.
In order to ensure that the clamping ring and the plates which make up the assemblies are accurately aligned, it has been a common expedient to use mating indexing vertical protrusions on the components, so that these vertical indexing projections will coact when assembly occurs, fixing the elements spatially relative to each other.
It is most desirable during the absorbence run that additional means be provided whereby the reading of the optical density of the cuvettes is accomplished for each cuvette at a fixed radial position, such position generally having been chosen at or near the exact center of the arcuate outer end wall of each cuvette. Also, it is desirable, if not essential, to provide each of the cuvettes with some identification means, such as numbers therefor, which enables the users thereof to program an electronic readout system and digital computer, or to program the electronic interfacing means for coaction with the computer, so as to identify the readings by cuvette number, such number identification of each cuvette being utilized with an automatic printout mechanism, all as described in the above references.
While various means for providing for such cuvette indentification and for the timed reading thereof have been used in the past, the most commonly used system is one in which the rotor holder for the cuvette array has positioned thereon, or associated physically therewith, some form of encoding system, which may consist of an optically transmissive annular series of slots, each of which is positioned opposite the center of each cuvette when the cuvette is aligned in, and supported by, the rotor holder. This series of indexing slots or other such means may be used to locate the particular cuvette area which is being measured; i.e., which is passing through the main optical path during the rotation of the run cycle. Alternatively suggested by the prior art have been systems incorporating a second disc mounted on the rotor shaft, this second disc having optical passageways, or magnetic markings, aligned with the cuvettes thereabove. There have also been suggested systems in which reflectors have been used for the encoding or position-identifying means. Such systems have invariably been either inaccurate or very elaborate as to their structure. Furthermore, such misalignment as is present will be repeated for each cuvette; i.e., if the rotor holder or second disc are angularly displaced five degress relative to the cuvettes of the disc, then each cuvette chamber will be displaced 5.degree. , resulting in totally inaccurate readings. It has, therefore, been recognized by the prior art workers that it would be ideal if the cuvette array utilized in the system could be made more accurate, less complex and less expensive by using inexpensive materials and methods of manufacturing, eliminating the machine tooling used by the prior art in order to provide structures possessing reproducibility sufficiently accurate for each analytical run. These prior art workers have also emphasized that it is essential, in order to obtain adequately accurate readings, that these parts, even after initial accurate alignment, must not move relative to each other during the entire centrifugation, from the inception to the completion of the analytical run, in order to avoid the introduction of new errors resulting from such relative displacement of the parts.
The prior art workers have mentioned also the desirability of the use of disposable, less expensive cuvette arrays, but have stated that this is not possible, because the disclosed prior art systems could not utilize such simple, inexpensive, disposable array and still provide the essential accurate stability of measurements which is required. This has been emphasized as to impracticality when it is realized that the microliter amounts of reagents used in the overall systems of such analyzers must have optical density cyclical measurements thereof determined by mechanical and electrical means which will produce a final series of electronically corrected signals from the computer to a printing mechanism, for which corrections should have been made for each of the following possible sources of errors: cuvette-to-cuvette non-uniformity as to size, radial or axial positioning, or thickness of the radiation permeable walls (e.g., non-uniform light transmission characteristics), variance in the intensity of the light source illuminating the optical path which the cuvettes intercept during reading, variation in the length of this optical path, non-uniform pulse reading times, programmed changes in rotor speed, radial displacement of the entire disc and rotor relative to the optical path, inherent variations in the rotor speed caused by changes in the voltage supplied to the motor drive of the rotor, non-uniform gain control of the electronic components, radial displacement of the positioning of the rotor holder relative to the cuvette array, random movement of the materials which react within the individual cuvettes during the run and read cycle, variations in the temperture and other environmental characteristics which cause differential expansion of the cuvette array and the rotor and cause changes in the reaction rate under which the analyses are performed, a high background noise to optical density ratio, as well as voltage or other variations in these correcting systems, and correction means for error compensation which are caused by either too rapid correction or slow reaction so that hunting will occur when the correction means operate. These systems of the prior art have, therefore, been non-accurate.
It is, therefore, a principle object of the present invention to provide inexpensive, disposable, rotatable cuvette array structures of generally disc-shaped, annular form, Which are much less expensive than any of those suggested in the prior art, and at the same time automatically eliminate a number of the above described errors inherent to the prior art, thereby reducing the complexity of the necessary prior art eleborate correction systems, so that the final system readout of the analytical run is more accurate than is possible with the prior art systems, even though it is much less complex in array structure.
Such results are obtained by the provision of unique structures including a number of unique, coating components of the rotary disc array.
It is, hence, an object of the invention to provide such an inexpensive, rotary cuvette array which provides at least as great accuracy as the previously known systems, and generally provides much greater accuracy, by the provision of geometrical fixation of previously known error sources by the spatially fixed relation of the various array components and including their configuration. Various modifications of sealing means for the cuvette are disclosed.
While the machine, system, and process described in the aforesaid applications in detail are the preferred overall systems in which the cuvette arrays of the present invention may be utilized, it is to be understood that, with very minor or with no alterations, the particular structures described and claimed in detail herein are capable of adaptive usage in many of the prior art systems.